1. Field of the Invention
The present invention relates generally to vehicle lift systems. More particularly, the invention concerns a battery-operated vehicle lift system configured for wireless charging.
2. Description of the Prior Art
The need to lift a vehicle from the ground for service work is well established. For instance, it is often necessary to lift a vehicle for tire rotation or replacement, steering alignment, oil changes, brake inspections, exhaust work, and other automotive maintenance. Traditionally, lifting a vehicle has been accomplished through the use of equipment that is built-into a service facility, such as either lift units with hydraulic actuator(s) installed below the surface of the floor or two and four-post type lift systems installed on the floor surface. These built-in units are located at a fixed location at the service facility and adapted to engage a vehicle frame to lift the vehicle from the ground.
In an effort to increase the versatility and mobility of lift devices and to reduce the need to invest in permanently mounted lifting equipment, devices commonly known as a mobile column lifts (MCLs) have been developed. An example of MCLs incorporated in a wireless portable vehicle lift system 20 is illustrated in FIG. 1, which illustrates a vehicle lift system 20 with four individual lifts 22 for lifting a vehicle. Although FIG. 1 depicts a four lift system, any combination of two or more lifts 22 may be used. It should also be understood that lift system 20 is not limited for use with vehicles, but also may be used to raise or lower other objects relative to a floor or ground surface, such as aircraft, industrial machinery, shipping containers, construction subassemblies, and the like.
An example of a vehicle lift 22 included in such a vehicle lift system 20 is illustrated in more detail in FIGS. 2, 3A, and 3B. The vehicle lift 22 illustrated in FIGS. 2, 3A, and 3B is similar to vehicle lifts described in U.S. Patent App. Publ. No. 2013/0240300, which is incorporated herein by reference in its entirety. With reference to FIG. 2, the vehicle lift 22 broadly includes a base 30, a post 32, a carriage assembly 34, a lift actuator 36, and a main housing 38. The base 30 supports the lift 22 on the floor or the ground. The post 32 is rigidly coupled to the base 30 and extends upwardly therefrom. The carriage assembly 34 is configured to engage a wheel of a vehicle and is vertically shiftable relative to the post 32. The lift actuator 36 is received in the post 32 and is operable to vertically raise and lower the carriage assembly 34 relative to the post 32 and the base 30. The main housing 38 is attached to the post 32 and encloses many of the components of that make up the control and power systems of the lift 22. The main housing 38 may also include a removable access panel 40 for providing access to various components of the lift's 22 control and power systems.
FIGS. 3A and 3B provide a view of the back of the lift 22. FIG. 3B shows the access panel 40 being removed and a lower portion of the main housing 38 cut away to show certain internal components located in the upper portion of the main housing 38. The lift 22 may generally include an electrical power supply, an electronic control system, and a hydraulic power system. More specifically, FIG. 3B shows that the electrical power supply system of the lift 22 can include two rechargeable batteries 42 (e.g., 12 VDC lead-acid batteries), a battery charger 44, and a main power switch 46; the electronic control system of the lift 22 can include a modular control unit 48 (e.g., with a touchscreen display 49) and a communications antenna 50; and the hydraulic power system of the lift 22 can include a hydraulic reservoir 52, a hydraulic pump 54, a hydraulic cylinder (not shown), and a plurality of hydraulic valves (not shown. The electronic control system can be used to control the hydraulic power system so as to control the raising and lowering operations of the lift 22.
The electrical power supply system (including the batteries 42) is configured to provide power to the individual systems of the lift 22, including the electronic control system and the hydraulic power system. As such, the electrical power supply system provides the electrical power necessary to control and operate the lifts 22. Generally, the batteries 42 of the electrical power supply system require frequent charging, so as to maintain sufficient charge to provide continued functionality of the lift 22 throughout a working day. However, it can be difficult keep the lift 22 physically coupled with a standard recharging power source, such as a mains power outlet, because the lift 22 is mobile and may be used in locations out of range of such standard recharging power sources. Furthermore, in some instances, the electrical cords generally used to electrically connect recharging power sources with the lift 22 may interfere with the operation and/or mobility of the lift 22, or may otherwise interfere with the maintenance being performed on the vehicle being raised by the lift. 22.
Accordingly, there exists a need for a vehicle lift 22 configured for wireless charging, such that the lift 22 can be continuously charged while the lift 22 is out of range of a physical recharging power source or when it is otherwise impractical to use a physical recharging power source. Although certain types of wireless power transfer devices have been used in the past for charging small-sized batteries (e.g., as may be used in small, handheld computing devices), such previously-used wireless power transfer devices have generally been restricted to transferring electrical power over small distances (i.e., over the near-field). The near-field refers to a region around a wireless power transfer device's antenna where magnetic fields and electric fields exist independently (i.e., generally a distance less than one or two wavelengths of the emitted electromagnetic signal). Because the magnetic and electric fields exist independently within the near-field, interferences within the emitted electromagnetic field are high such that signals degrade quickly and are not useful for transferring power outside of the near-field. Regardless over the relatively short near-field, wireless power transfer devices are capable of facilitating generally high electrical power transfer via magnetic induction and/or capacitive coupling. Wireless power transfer device antennas that operate in the near-field (via magnetic induction and/or capacitive coupling) are not required to be very large, such that the antennas are easily incorporated into power transfer devices and into handheld computing devices. As such, most previously-used wireless power transfer devices have been used to re-charge the batteries of small, handheld computing devices, such as a smart-phones and tablets over relatively short distances (i.e., the near-field).
To accomplish wireless power transfer over longer distances (i.e., beyond the near-field), power transfer must be completed in the far-field, which refers to distances greater than two wavelengths of the electromagnetic signal that is emitted from the transmitting antenna. However, most previously-used wireless power transfer devices are not configured to operate in the far-field. In more detail, to operate in the far-field, the transmitting and receiving antennas are generally required to be much larger than those smaller antennas used for operating in the near-field. Specifically, the amount of power emitted as an electromagnetic signal in the far-field by a transmitting antenna depends on a ratio of the antenna's size to the wavelength of the signal. For large wavelength signals transmitted by relatively-small antennas, generally little power is radiated. For instance, with the near-field power transmissions devices discussed above, which use generally small antennas, almost none of the energy is emitted in the far-field as electromagnetic radiation. On the other hand, relatively-larger antennas (i.e., antennas generally the same size as the signal's wavelength) can radiate power more efficiently in the far field. Nevertheless, the electromagnetic signals radiated by such fair-field-capable antennas radiate such signals in all directions (i.e., omni-directionally). As a result, the amplitude of the electromagnetic signal falls off proportionally with distance, such that the available energy per unit area falls off proportionally with a square of the distance. Thus, if the transmitting and receiving antennas are far apart, only a small amount of the emitted radiation will be available to be received by the receiving antennas for conversion to power. Because of these difficulties, wireless power transfer over the far-field has received little attention or implementation.
As such, there is a need for a vehicle lift system configured to provide wireless charging to the lift 22 such that the batteries 42 of the lifts 22 can remain sufficiently charged even when the lifts 22 are out of range of a physical recharging power source or when it is otherwise impractical to use a physical recharging power source. Furthermore, there is a need for a wireless charging system for vehicle lifts that provides efficiently wireless charging over the near-field and far-field.